1. Technical Field of the Invention
This invention is related to architecture for a publicly accessed wireless local area network that provides for seamless mobility between access points on the wireless local area network. The invention provides for differing levels of mobile subscriber services and packet level authentication and encryption. The architecture can be supported on existing local area networks and allows virtual operators to oversee the operation of the wireless local area network. The invention also provides for a method of operating the publicly accessed wireless local area network and its control and data protocols.
2. Description of the Related Art
There will now be provided a discussion of various topics to provide a proper foundation for understanding the invention.
The rapid evolution of Internet services and wireless technologies have stimulated the development of both cellular mobile and wireless LAN (WLAN) access systems for the wireless Internet, thereby providing users convenient Internet access and location-sensitive applications. Most existing WLAN access systems are either private, as in company or campus networks, or by subscription to the services of a WLAN operator.
Public services operators are being attracted to this type of private networking (enterprise LAN), both wired and wireless, in order to provide the capacity and performance expected by their customers. For a broad range of evolving Internet applications, including Internet audio and video multicasting and interactive multimedia applications, high speed and low delay are essential. The public cellular mobile network cannot fully meet this demand, even with the proposed enhancements of third generation (3G) mobile communication systems providing downstream burst rates up to 384 kbps outdoors and 2 Mbps rate indoors. These rates are a significant improvement over second-generation systems, and MIMO (multiple antennas) technology may significantly increase spectral efficiency. However, bandwidth will still be limited and costs will be high due to the huge monetary amounts paid by operators in spectrum auctions. This is an intrinsic problem because the 3G mobile system, like the 2G system, aims to provide continuous coverage in reserved spectrum. The capacity of the system is unlikely to be scalable to the investment cost.
WLAN technology can and does provide Internet access at low cost and with high capacity. It uses “free” spectrum (although, as described later, it may also implement cellular mobile microcells in reserved spectrum), is scalable, and is easily integrated into the wired network. There is a potential problem with interference between WLANs in the unregulated spectrum. It will be incumbent upon property owners, e.g., airports and hotels where public access through WLANs will become serious business operations, to enforce spectrum compatibility. The interference problem between IEEE 802.11 and Bluetooth systems, both of which may be supported by a property owner, is being addressed in IEEE 802.15.
Despite their limitations, the existing WLAN hot spot solutions are acceptable for many applications, using commercial wireless LAN technology such as Nokia's Public Access Zone, Cisco's Aironet and Lucent's ORINOCO Public Access Solutions. The wireless operators include such companies as MobileStar Corporation, Wayport and Nomadix.
Referring to FIG. 1, a conventional GSM cellular mobile system is illustrated. The GSM system comprises a hierarchical architecture comprised of a mobile switching center (MSC) 102 that is coupled to a base station 103 via circuit-switched networks. The mobile switching center 102 could also be coupled to other mobile switching centers as well as well as other base stations (not shown). The base station 103 comprises a base station controller (BSC) 104 and a plurality of base station transceivers (BTS) 105-1, 105-2, 105-n, where n is the number of base station transceivers connected to the base station controller 104. The mobile switching center 102 is coupled to a public switched telephone network (PTSN) interface 101. The mobile switching center 102 is coupled to a home location register (HLR) 106, a virtual location register (VLR) 107 and an equipment identity register (EIR) 108. The home location register 106 is also connected to an authentication center 109.
As illustrated in FIG. 1, the Generalized Packet Radio Service (GPRS), which is the data service version of GSM, uses a hierarchical architecture as well. A gateway GPRS/3G support node (GGSN) 110 is coupled to the home location register 106 and the Internet interface 116. The serving GPRS/3G support node (SGSN) 111 is coupled to the gateway GPRS/3G support node 110, the home location register 106 and the equipment identification register 108. The gateway GPRS/3G support node 110 and the serving GPRS/3G support node 111 are in a packet-switched domain and comprise the IP multimedia subsystem. The serving GPRS/3G support node 111 is coupled to the base station 103 via a packet-switched network. The serving GPRS/3G support node 111 is also coupled to a radio network base station 112 via the packet-switched network. The radio network base station 112 comprises a radio network controller 114 that is coupled to a plurality of base station transceivers 115-1, 115-n, where n is the number of base station transceivers. The architecture illustrated in FIG. 1 provides a core network that carries centralized traffic flows of circuit-switched voice, packet-switched data and IP multimedia traffic.
However, some standards bodies and forums are embracing the concept of a distributed IP-based mobile communications system without centralized traffic bottlenecks. Note that it is only the routings of mobile subscriber data that are presumed to be distributed. Control functions such as mobility management, authorization, authentication, accounting and directory services may or may not be distributed. The organizations include the Third Generation Partnership Project 2 (3GPP-2), the Internet Engineering Task Force (IETF), the Mobile Wireless Internet Forum (MWIF), and the IMT-2000 organization of the International Telecommunications Union (ITU).
Referring to FIG. 2, the 3GPP-2 network architectures based on IETF's mobile IP model are illustrated. In this architecture, there is no core network for mobile systems as illustrated in FIG. 1. Instead, a 2G system 201 comprising a home location register (HLR) 202 and a virtual location register (VLR) 203 is coupled to a radio network (RN) 204. The radio network 204 comprises a radio resource controller 206 (RRC) and a packet control function (PCF) device 205. The 2G system 201 is coupled to the radio resource controller 206. Internet appliance 207 can be coupled to the radio resource controller 206 as well. The radio network 204 in the 3GPP-2 architecture directly connects to a gateway (PDSN) 208 that is connected to an IP network 209, e.g., a LAN, MAN or WAN. A user home network 210 can be reached via the IP network 209. In addition, a wireless LAN (WLAN) 212 could also be coupled to the IP network 209 via a second gateway (PSDN) 211. Non-IP voice traffic has a direct path from the radio resource controller 206 to the public switched telephone network 213 (PSTN), so that the 2G voice network is maintained as an entity within 3G networks.
In addition, an IP-based mobility system is extensible, through the Internet, to outlying or temporary cellular mobile base stations and to WLANs. WLANs supporting 3G air interfaces, as well as IEEE 802.11, HiperLAN-2, and Bluetooth air interfaces, may some day be used for broadband access in public hot spots and in corporate and residential settings.
One disadvantage of present-day WLAN access services is the lack of public access, in that access to the WLAN is restricted to the subscribers of the specific WLAN operator. Another disadvantage is that a subscriber could be tied to a single access point. This has the potential of discouraging applications such as listening to Internet radio while wandering through a shopping mall. Another disadvantage is the potential restriction to a single WLAN air interface, thereby reducing the range of appliances, including those with cellular mobile air interfaces, that it would be desirable to support.